The complex originally housed the UK’s first fast fission reactor Zephyr, followed by Dimple – a multi-purpose, zero power, water moderated reactor. These played a central role in providing the data measurements used to support the first generation of nuclear reactor designs. In its latter years, the building hosted research into prosthetic limbs and vehicle emissions under AEA Technology.
Demolition works began in August 2024 with the safe removal of over 19 tonnes of asbestos waste. The building’s final structure was razed to the ground in March 2025, followed closely by the removal of its sub-structure base slab and two four-metre-deep underground basements that once housed some of the reactor and drainage systems.
Mid demolition
A comprehensive radiological survey confirmed the absence of contamination, enabling the one-metre-deep demolition void to be filled with over 500 tonnes of locally sourced topsoil safely and efficiently.
Rob Squires, Harwell site delivery manager, said
This fantastic achievement marks a significant milestone in the evolution of Harwell Campus. Removing this complex has cleared a 1,498m2 footprint ready for its next use and honoured the legacy of the groundbreaking work that once took place within its walls.
In total, 232 lorry movements removed almost 4,000 tonnes of re-useable demolition waste from the site and delivered 528 tonnes of topsoil. A scrap metal contract also raised almost £30,000 income to offset decommissioning costs.
The final remediation works – including improvements to the North Apron Pavement – were completed two days ahead of schedule on 16 July 2025.
The project was delivered in partnership with KDC Veolia, part of the Celadon Alliance, under the NRS demolition and remediation framework contract. Their proactive approach to safety, environmental compliance, and collaborative working helped ensure zero lost time accidents throughout the project.
Base slab demolition
Doug Fox, acting project manager, KDC Veolia, said
This demolition project has been a true pleasure to deliver alongside the NRS team. Through our strong partnership approach, we combined specialist equipment – including a low-impact wheeled excavator – with careful topsoil management to ensure efficient and sustainable project delivery.
This successful outcome demonstrates what is achievable when teams work together to maintain high environmental and safety standards.
As Harwell continues to evolve, the successful completion of this project reflects the commitment to safe, sustainable transformation across the site.
